THE BEHAVIOR OF D-GLUCURONIC, D-GALACTURONIC, AND D-MANNURONIC ACID IN DILUTE AQUEOUS SODIUM HYDROXIDE

Two percent aqueous sodium hydroxide at room temperature, preferably for 24 hours, was used to obtain the Lobry de Bruyn – van Ekenstein transformation products. The transformations proceeded much more slowly than in the case of the hexoses; complex changes in specific rotation occurred, and equilibrium among the products was not attained, probably because acidic non-reducing substances formed at a comparable rate. After 24 hours, 39% of D-glucurone was recovered unchanged, together with 9% of D-mannuronic acid and 2% of keto acid probably based on fructose. D-Mannurone gave the same products, but unchanged starting material once more predominated. D-Galacturonic acid was recovered in 58% yield together with 12% of D-taluronic acid, a new substance characterized as a crystalline mono-hydrated brucine salt. A trace of a keto acid, presumably derived from D-tagatose, was also formed.